Polishing pad

ABSTRACT

A polishing pad of the present invention contains a water-insoluble matrix material comprising a crosslinked polymer such as a crosslinked 1,2-polybutadiene and water-soluble particles dispersed in the material, such as saccharides. The solubility of the water-soluble particles in water is 0.1 to 10 wt % at 25° C., and the amount of water-soluble particles eluted from the pad when the pad is immersed in water is 0.05 to 50 wt % at 25° C. Further, in the polishing pad of the present invention, the solubility of the water-soluble particles in water is 0.1 to 10 wt % at 25° C. at a pH of 3 to 11, and solubility thereof in water at 25° C. at a pH of 3 to 11 is within ±50% of solubility thereof in water at 25° C. at a pH of 7. In addition, the water-soluble particles contain an amino group, an epoxy group, an isocyanurate group, and the like. This polishing pad has good slurry retainability even if using slurries different in pH and also has excellent polishing properties such as a polishing rate and planarity.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a polishing pad. Morespecifically, it relates to a polishing pad which has good slurryretainability, a high degree of hardness, and excellent polishingproperties such as a capability of forming a polished surface withsufficient planarity.

[0003] The polishing pad of the present invention is widely used forpolishing the surfaces of semiconductor wafers and other materials.

[0004] 2. Description of the Prior Art

[0005] As a polishing method capable of forming a polished surface witha high degree of planarity, CMP (Chemical Mechanical Polishing) has beendrawing attention in recent years. In CMP, a surface to be polished ispolished by sliding or rotating a polishing pad and the surface againsteach other with a slurry which is a water-based dispersion havingabrasives dispersed therein caused to flow down on the surface of thepolishing pad.

[0006] One of factors which significantly affect productivity in thisCMP is a polishing rate. This polishing rate can be significantlyimproved by increasing the amount of a retained slurry from aconventional amount.

[0007] In CMP, heretofore, a polyurethane foam containing fine airbubbles is used as the polishing pad, and polishing is carried out witha slurry retained in pores opened on a surface of this polishing pad.

[0008] However, it is difficult to control the degree of foaming in thepolyurethane foam to a desired degree, and it is very difficult tocontrol the sizes of the air bubbles, a foaming density and otherproperties uniformly throughout the foam. Consequently, the quality ofthe polishing pad comprising the polyurethane foam varies, therebycausing a variation in the polishing rate and other properties.

[0009] JP-A 8-500622, JP-A 2000-34416 and JP-A 2000-33552 (the term“JP-A” as used herein means an “unexamined published Japanese patentapplication”) disclose various resins having water-soluble materialsdispersed therein as polishing pads whose pores can be controlled moreeasily than the above polishing pad comprising the foam. Of thesepublications, the former two publications describe the effectiveness ofa polishing pad containing a water-soluble material. Further, in thelast publication, a material of a matrix material is studied, and apolishing pad for which more stable polishing and an improvement inpolishing rate are recognized is disclosed. However, the slurryretainability and polishing rate of the polishing pad are notnecessarily satisfactory.

[0010] Furthermore, slurries having different pHs in a wide range of pHshave heretofore been used, and a polishing pad capable of adapting tothese various slurries different in pH has been desired.

SUMMARY OF THE INVENTION

[0011] The present invention has been conceived in view of the abovecircumstances.

[0012] An object of the present invention is to provide a polishing padwhich shows a high polishing rate since it is excellent in slurryretainability over a wide pH range even if various slurries havingdifferent pHs are used; has a high degree of hardness; can form apolished surface having sufficient planarity; and can effectivelyprevent deterioration in the slurry retainability and polishing rateduring polishing and after dressing.

[0013] Other objects and advantages of the present invention will beapparent from the following description.

[0014] The present inventors have intensively studied a mechanism ofgradual deterioration in slurry retainability and polishing rate duringpolishing and a mechanism of formation of pores on the surface of apolishing pad by use of a diamond whetstone (surface conditioning) orformation of pores in dressing which reconditions the surface of thepolishing pad. As a result, it has been found that when shearing stressis exerted on the surface of a conventional polishing pad by the abovepolishing and dressing, a matrix material which is a main constituent ofthe pad undergoes elongation, followed by plastic deformation, wherebypores are blocked. Further, it has also been found that the pores areblocked by not only polishing dust from a polished surface but alsopolishing dust from the matrix material itself. That is, it has beenrevealed that these causes make it difficult to maintain a polishingrate. As a method of solving them, use of a material having acrosslinked structure which exhibits an elasticity restoration propertyas the matrix material is effective. More stable polishing has beendesired, and further improvements in slurry retainability and polishingrate have also been desired. The present invention has been completedbased on these findings and desires.

[0015] That is, according to the present invention, firstly, the aboveobject and advantages of the present invention are achieved by apolishing pad which comprises a water-insoluble matrix materialcomprising a crosslinked polymer and water-soluble particles dispersedin the water-insoluble matrix material, wherein the solubility of thewater-soluble particles in water is. 0.1 to 10 wt % at 25° C., and theamount of water-soluble particles eluted from the pad when the pad isimmersed in water is 0.05 to 50 wt % at 25° C.

[0016] Further, according to the present invention, secondly, the aboveobject and advantages of the present invention are achieved by apolishing pad which comprises a water-insoluble matrix materialcomprising a crosslinked polymer and water-soluble particles dispersedin the water-insoluble matrix material, wherein the solubility of thewater-soluble particles in water is 0.1 to 10 wt % at 25° C. at a pH of3 to 11, and solubility thereof in water at 25° C. at a pH of 3 to 11 iswithin ±50% of solubility thereof in water at 25° C. at a pH of 7.

[0017] Further, according to the present invention, thirdly, the aboveobject and advantages of the present invention are achieved by apolishing pad which comprises a water-insoluble matrix materialcomprising a crosslinked polymer and water-soluble particles dispersedin the water-insoluble matrix material, wherein the water-solubleparticles contain at least one group selected from the group consistingof an amino group, an epoxy group, an isocyanurate group and a hydroxylgroup.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a graph showing that the water solubility at 25° C. ofβ-cyclodextrin coupled with γ-(2-aminoethyl)-aminopropyltrimethoxysilaneis hardly changed by pH.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, the present invention will be described in detail.

[0020] The above “water-insoluble matrix material” (hereinafter may alsobe simply referred to as “matrix material”) contains a crosslinkedpolymer.

[0021] The above “crosslinked polymer” constitutes the matrix materialand imparts an elasticity restoration property to the matrix material byhaving a crosslinked structure. By containing the crosslinked polymer,displacement caused by shearing stress exerted on a polishing pad duringpolishing can be kept small, and it can be effectively inhibited thatthe matrix material is drawn excessively and undergoes plasticdeformation during polishing and dressing, thereby blocking pores, andthat the surface of the polishing pad becomes too fuzzy. Therefore,pores can be formed efficiently, deterioration in slurry retainabilityat the time of polishing is little, fuzz hardly occurs, and inhibitionof polishing planarity is avoided.

[0022] Illustrative examples of such a crosslinked polymer include acrosslinked polymer resulting from crosslinking an uncrosslinked polymersuch as a thermoplastic resin, an elastomer, a crude rubber or a curableresin, i.e., a resin curable by heat or light such as a thermosettingresin or photocurable resin, and a crosslinked polymer resulting fromco-crosslinking a mixture of at least two of the above uncrosslinkedpolymers. Further, crosslinking may be performed on a portion or thewhole of the polymer. Further, in the former crosslinking, a mixturecomprising a partially crosslinked polymer and an uncrosslinked polymeror a mixture comprising a wholly crosslinked polymer and anuncrosslinked polymer may be produced. A method of carrying out thecrosslinking may be chemical crosslinking by use of a crosslinking agentor radiation crosslinking through irradiation of ultraviolet radiationor an electron beam.

[0023] As a crosslinking method, chemical crosslinking using acrosslinking agent is preferred. Illustrative examples of thecrosslinking agent include sulfur and an organic peroxide. For polishinga semiconductor, the organic peroxide is preferred since impurities suchas sulfur are detrimental to the semiconductor. Specific examples of theorganic peroxide include dicumyl peroxide, di-t-butyl peroxide, diethylperoxide, diacetyl peroxide and diacyl peroxide. They may be used aloneor in admixture of two or more. These crosslinking agents are preferablyused in an amount of not larger than 5 wt %, more preferably 0.01 to 4wt %, particularly preferably 0.1 to 3 wt %, based on a crosslinkable(co)polymer.

[0024] At this point, a polymer crosslinked in advance may be mixed, anda crosslinking reaction may be carried out in the co-presence of such acrosslinking agent as described above in a step to be described later ofmixing a water-insoluble matrix with water-soluble particles.

[0025] Specific examples of the thermoplastic resin include a1,2-polybutadiene resin; an ethylene-vinyl acetate copolymer such as EVAcontaining 3 wt % or more of vinyl acetate units; polyolefin resins suchas a polyethylene; an acrylonitrile-styrene-butadiene copolymer such asan ABS resin; a polystyrene resin; a polyacryl resin such as a(meth)acrylate resin; vinyl ester resins other than EVA; a saturatedpolyester resin; a polyamide resin; a fluororesin such as apolyvinylidene fluoride; a polycarbonate resin; and a polyacetal resin.

[0026] Specific examples of the elastomer include polyolefin-basedelastomers (excluding EVA); styrene-based elastomers such as astyrene-butadiene-styrene copolymer and a hydrogenated block copolymer(SEBS) thereof; thermoplastic-polyurethane-based elastomers;thermoplastic-polyester-based elastomers; polyamide-based elastomers;silicone-resin-based elastomers; and fluorocarbon-resin-basedelastomers.

[0027] Specific examples of the rubber include butadiene-based rubberssuch as a high cis-butadiene rubber and a low cis-butadiene rubber;conjugated-diene-based rubbers such as an isoprene-based rubber, astyrene-butadiene-based rubber and a styrene-isoprene-based rubber;nitrile-based rubbers such as an acrylonitrile-butadiene-based rubber;acrylic rubbers; ethylene-α-olefin-based rubbers such as anethylene-propylene-based rubber and an ethylene-propylene-diene-basedrubber; and other rubbers such as a butyl rubber, a silicone rubber anda fluorine rubber.

[0028] Specific examples of the curable resin include an urethane resin,an epoxy resin, a (meth)acrylic resin, an unsaturated polyester resin, apolyurethane-urea resin, an urea resin, a silicon resin and a phenolicresin.

[0029] Of these crosslinked polymers, crosslinked polymers resultingfrom crosslinking of the 1,2-polybutadiene resin, ethylene-vinyl acetatecopolymer, polyethylene resin, acrylonitrile-styrene-butadienecopolymer, styrene-butadiene-styrene copolymer, polyacryl resin, vinylester resin, saturated polyester resin, polyamide resin and polyacetalresin are preferred. In addition to these crosslinked polymers,crosslinked polymers resulting from co-crosslinking of two or more ofthese resins are also acceptable. These crosslinked polymers have asignificant effect of improving moldability and abrasion resistance.Further, they hardly undergo softening caused by water absorption andare stable against acid and alkali contained in a slurry.

[0030] These crosslinked polymers may be contained in a matrix materialalone or in combination of two or more.

[0031] Of these materials having a crosslink structure, a crosslinked1,2-polybutadiene is preferred since it is stable against strong acid orstrong alkali contained in various slurries for chemical machinerypolishing and hardly undergoes softening caused by water absorption. Thecrosslinked 1,2-polybutadiene can be used solely or in admixture withotter materials. Preferred examples of the other materials which can beused in admixture with the crosslinked 1,2-polybutadiene include abutadiene rubber and an isoprene rubber. The content of the crosslinked1,2-polybutadiene when it is used in the form of a mixture is preferablynot lower than 30 wt %, particularly preferably not lower than 50 wt %.

[0032] Further, the matrix material may have a functional group such asan acid anhydride group, a carboxyl group, a hydroxyl group, an epoxygroup or an amino group. By causing the matrix material to have such afunctional group, the affinity of the matrix material for water-solubleparticles and a slurry can be adjusted. When the water-soluble particleshave a functional group such as an amino group, an epoxy group, anisocyanurate group or a hydroxyl group as will be described later, thematrix material containing a functional group and the water-solubleparticles having a functional group are preferably not reacted to suchan extent that a given amount of the water-soluble particles are eluted.

[0033] The matrix material preferably has an elongation which remainsafter fracture (hereinafter simply referred to as “residual elongationafter fracture”) of not higher than 100% according to JIS K6251 when atest piece comprising the matrix material is fractured at 80° C. Inother words, a total gauge length after fracture is preferably at mosttwice or less as long as a gauge length before fracture. The residualelongation after fracture is preferably not higher than 30%, morepreferably not higher than 10%, particularly preferably not higher than5%. It is generally higher than 0%. When the residual elongation afterfracture exceeds 100%, fine pieces scratched or stretched out of thesurface of a polishing pad during polishing or restoration of thesurface are liable to block pores undesirably.

[0034] The above “residual elongation after fracture” is an elongationresulting from subtracting a gauge length before a tensile test from thetotal of lengths from gauge lines to fractured points of fractured anddivided test pieces when a dumbbell-shaped test piece No. 3 is fracturedin the tensile test at a tensile rate of 500 mm/min and a testingtemperature of 80° C. in accordance with a “tensile test method ofvulcanized rubber” JIS K 6251. Further, the test is carried out at 80°C. since sliding or rotating causes heat in actual polishing.

[0035] Further, the water content of the matrix material is preferablynot higher than 3%, more preferably not higher than 2%, particularlypreferably not higher than 1%. When the water content is not higher than3%, swelling of the water-soluble particles in the polishing pad issuppressed to a sufficient degree, thereby allowing the pad to have ahigh degree of hardness, and polishing properties such as in-planeuniformity and local planarity are improved. When the water content ofthe matrix material exceeds 3%, the water-soluble particles in thematrix material may be dissolved and/or swollen, and polishingproperties such as in-plane uniformity and local planarity may bedegraded undesirably.

[0036] The above water-soluble particles leave the matrix material whenthe polishing pad makes contact with water and/or a slurry which is awater-based dispersion at the time of polishing. Particularly,water-soluble particles present in the vicinity of the outermost layerof the polishing pad are eluted, whereby pores are formed. These poresserve to hold the slurry and hold polishing dust temporarily. Thewater-soluble particles dispersed in the matrix material not onlydissolve and leave the matrix material upon contact with water but alsomay absorb water, swell and leave the matrix material in the form of agel. Further, in addition to water, the water-soluble particles alsodissolve or swell and leave the matrix material by contacting with awater-based mixed medium containing an alcohol-based solvent such asmethanol.

[0037] The water-soluble particles may be organic or inorganicwater-soluble particles. Of the two, th organic water-soluble particleshaving low solubility in water are generally preferred. Specificexamples of the organic water-soluble particles include particles ofsaccharides (polysaccharides, e.g., α, β or γ-cyclodextrin, dextrin andstarch, lactose, mannite, and the like), celluloses (hydroxypropylcellulose, methylcellulose, and the like), proteins, a polyvinylalcohol, a polyvinyl pyrrolidone, a polyacrylic acid, a polyacrylate, apolyethylene oxide, water-soluble photosensitive resins, a sulfonatedpolyisoprene, and a sulfonated polyisoprene copolymer. Of these,particles containing hydroxyl groups are particularly preferred.Further, as inorganic water-soluble particles which have low watersolubility and can be used in the present invention, particles ofcalcium sulfate can be named, for example. In addition, particles ofmagnesium sulfate having higher solubility can also be used once thesolubility which is lowered to a proper range by incorporating, forexample, amino groups into the particles.

[0038] These water-soluble particles may be contained in the matrixmaterial solely or in combination of two or more.

[0039] Further, the average particle diameter of these water-solubleparticles is preferably 0.1 to 500 μm, more preferably 0.5 to 100 μm.When the average particle diameter is smaller than 0.1 μm, pores whichare smaller in size than abrasives to be used are formed, so that itbecomes liable to be difficult to obtain a polishing pad capable ofholding a slurry satisfactorily. Meanwhile, when it is larger than 500μm, the pores to be formed become so large that the mechanical strengthand polishing rate of the polishing pad to be obtained are liable todeteriorate. Particle size distribution is not particularly limited, andparticle diameters may be uniform or non-uniform. Further, the shapes ofthe water-soluble particles are not particularly limited. They may be inthe form of plates, grains, spheres, spindles or needles or may beamorphous or may take any other forms.

[0040] The content of these water-soluble particles in the polishing padis preferably 0.1 to 90 vol %, more preferably 1 to 60 vol %,particularly preferably 2 to 40 vol %, based on the total of the matrixmaterial and the water-soluble particles which is 100 vol %. When thecontent of the water-soluble particles is lower than 0.1 vol %, poresare not formed sufficiently in the polishing pad to be obtained, so thatthe polishing rate is liable to drop. Meanwhile, when the content of thewater-soluble particles is higher than 90 vol %, it is liable to becomedifficult to fully prevent swelling or dissolution of the water-solubleparticles existing in the polishing pad to be obtained, and it becomesdifficult to keep the hardness and mechanical strength of the polishingpad at proper values.

[0041] Further, to the water-soluble particles, an epoxy resin, apolyimide, a polyamide, a polysilicate or various coupling agents may bephysically adsorbed or chemically bonded, for example. This ispreferable since moisture absorption by the water-soluble particles issuppressed thereby. It is preferred that an outer shell be formed on atleast a portion of the outermost portion of the water-soluble particleby the above material. In this case, moisture absorption by thewater-soluble particles is further suppressed. Of the above materials,the coupling agents are more preferable, and of the coupling agents, acoupling agent having an amino group, an epoxy group or an isocyanurategroup is particularly preferable.

[0042] Furthermore, the water-soluble particles can contain at least onefunctional group selected from the group consisting of an amino group,an epoxy group, an isocyanurate group and a hydroxyl group. In thiscase, the functional groups can serve as a compatibility-imparting agentand/or a dispersion stabilizer for the matrix material and thewater-soluble particles, increase affinity between the matrix materialand the water-soluble particles and improve dispersibility of thewater-soluble particles in the matrix material. Thus, by improving thedispersibility of the water-soluble particles, a uniform polishing padcan be attained, and polishing properties such as in-plane uniformityand local planarity are improved.

[0043] As the functional group, the hydroxyl group is preferred asdescribed above. When the matrix material has a functional group such asan acid anhydride group, a carboxyl group, a hydroxyl group, an epoxygroup or an amino group as described above, the water-soluble particleshaving the functional group and the matrix material having thefunctional group are preferably not reacted to such an extent that agiven amount of the water-soluble particles are eluted.

[0044] Illustrative examples of the coupling agent containing at leastone group selected from an amino group, an epoxy group and anisocyanurate group include silane-based coupling agents, aluminum-basedcoupling agents, titanium-based coupling agents, and zirconia-basedcoupling agents. Of these, the silane-based coupling agents are oftenused. Of the silane-based coupling agents, an amino-group-containingsilane-based coupling agent, an epoxy-group-containing silane-basedcoupling agent and an isocyanurate-group-containing silane-basedcoupling agent are more preferred.

[0045] Specific examples of the amino-group-containing silane-basedcoupling agent include aminopropyltrimethoxysilane,aminopropyltriethoxysilane, aminopropyl(methyl)dimethoxysilane,aminopropyl(methyl)diethoxysilane,N-phenyl-γ-aminopropyltrimethoxysilane,N-butyl-γ-aminopropyltrimethoxysilane,N-β-(aminoethyl)γ-aminopropyltrimethoxysilane,N-β(aminoethyl)γ-aminopropyl(methyl) dimethoxysilane,N-β(aminoethyl)γ-aminopropyltriethoxysilane,N-(6-aminohexyl)γ-aminopropyltrimethoxysilane,N-(6-aminohexyl)γ-aminopropyl(methyl)dimethoxysilane,N-(6-aminohexyl)γ-aminopropyltriethoxysilane,N-[styryl(aminomethyl)]γ-aminopropyltrimethoxysilane,N-[styryl(aminomethyl)]γ-aminopropyl(methyl)dimethoxysilane,N-[styryl(aminomethyl)]γ-aminopropyltriethoxysilane,N[N-β(aminoethyl)aminoethyl-γ-aminopropyltrimethoxysilane,N[N-β(aminoethyl)aminoethyl]γ-aminopropyl(methyl)dimethoxysilane,N[N-β(aminoethyl)aminoethyl]γ-aminopropyltriethoxysilane,N[N-(benzylmethyl)aminoethyl]γ-aminopropyltrimethoxysilane,N[N-(benzylmethyl)aminoethyl]γ-aminopropyl(methyl)dimethoxysilane,N[N-(benzylmethyl)aminoethyl]γ-aminopropyltriethoxysilane,N[N-(benzyl)aminoethyl]γ-aminopropyltrimethoxysilane,N[N-(benzyl)aminoethyl]γ-aminopropyl(methyl)dimethoxysilane,N[N-(benzyl)aminoethyl]γ-aminopropyltriethoxysilane,N-phenylaminopropyltrimethoxysilane,N-phenylaminopropyl(methyl)dimethoxysilane,N-phenylaminopropyltriethoxysilane, N-phenylaminomethyltrimethoxysilane,N-phenylaminomethyl(methyl)dimethoxysilane,N-phenylaminomethyltriethoxysilane, bis(trimethoxysilylpropyl)amine,P-[N-(2-aminoethyl)aminomethyl]phenethyltrimethoxysilane,N-[(3-trimethoxysilyl)propyl]diethylenetriamine,N-[(3-trimethoxysilyl)propyl]triethylen tetramine, andN-3-trimethoxysilylpropyl-m-phenylenediamine.

[0046] Of these, aminopropyltrimethoxysilane,aminopropyltriethoxysilane,N-β-(aminoethyl)γ-aminopropyltrimethoxysilane,N-β(aminoethyl)γ-aminopropyl(methyl)dimethoxysilane andN-β(aminoethyl)γ-aminopropyltriethoxysilane are preferred.

[0047] Further, illustrative examples of the epoxy-group-containingsilane-based coupling agent include γ-glycidoxypropyltrimethoxysilane,γ-glycidoxypropyl(methyl)dimethoxysilane,γ-glycidoxypropyltriethoxysilane,γ-glycidoxypropyl(methyl)diethoxysilane, andβ-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.

[0048] Of these, γ-glycidoxypropyltrimethoxysilane andγ-glycidoxypropyltriethoxysilane are preferred.

[0049] Further, illustrative examples of theisocyanurate-group-containing silane-based coupling agent include(trimethoxysilylpropyl)isocyanurate, (triethoxysilylpropyl)isocyanurate,(triisopropoxysilylpropyl)isocyanurate,1,3-bis(trimethoxysilylpropyl)isocyanurate,1,3-bis(triethoxysilylpropyl)isocyanurate,1,3-bis(triisopropoxysilylpropyl)isocyanurate,1,5-bis(trimethoxysilylpropyl)isocyanurate,1,5-bis(triethoxysilylpropyl)isocyanurate,1,5-bis(triisopropoxysilylpropyl)isocyanurate,1,3,5-tris(trimethoxysilylpropyl)isocyanurate,1,3,5-tris(triethoxysilylpropyl)isocyanurate, and1,3,5-tris(triisopropoxysilylpropyl)isocyanurate.

[0050] Of these, 1,3,5-tris(trimethoxysilylpropyl)isocyanurate and1,3,5-tris(triethoxysilylpropyl)isocyanurate are preferred.

[0051] Thes coupling agents may be used alone or in combination of twoor more. Further, coupling agents containing different types offunctional groups can be used in combination.

[0052] A treatment using the coupling agent containing at least onegroup selected from an amino group, an epoxy group and an isocyanurategroup can be carried out by using the coupling agent in an amount ofpreferably not larger than 10 wt %, more preferably 0.01 to 10 wt %,much more preferably 0.01 to 5 wt %, based on the water-solubleparticles. By the treatment using the coupling agent, the water-solubleparticle contains at least one group selected from an amino group, anepoxy group and an isocyanurate group on the surface. Further, when theabove outer shell is formed, the above effect can still be achievedsufficiently even if the outer shell is formed only on a portion of thewater-soluble particle.

[0053] The solubility of the water-soluble particles in water (deionizedwater) at 25° C. is 0.1 to 10 wt %, preferably 0.2 to 8 wt %, morepreferably 0.5 to 5 wt %. When the solubility is lower than 0.1 wt %,elution of the water-soluble particles at the time of polishing isinsufficient, so that pores may not be able to be formed sufficientlyand the polishing rate may be decreased. Meanwhile, when the solubilityis higher than 10 wt %, the rate of elution to be described later of thewater-soluble particles from the polishing pad may exceed an upper limitundesirably. When the solubility is within the above range,water-soluble particles present in the vicinity of the outermost layerof the polishing pad of the present invention dissolve or swell andleave or free from the polishing pad when the polishing pad of thepresent invention makes contact with slurries during polishing, therebyfacilitating adequate formation of pores.

[0054] Further, when the water-soluble particles contain at least onegroup selected from an amino group, an epoxy group and an isocyanurategroup, solubility thereof in water can be lowered and adjusted to aproper range more easily. Further, the solubility of the water-solubleparticles in water at 25° C. at a pH of 3 to 11, preferably 1 to 13, ispreferably 0.1 to 3 wt %, particularly preferably 0.5 to 2.5 wt %. Whenthe solubility in water is low as described above, the degree of elutionwhich will be described later can be adjusted to a preferred rangeeasily, formation of pores inside the polishing pad can be prevented,the polishing pad can have sufficient hardness, and polishing propertiessuch as in-plane uniformity and local planarity are improved.

[0055] The solubility of the water-soluble particles in water at a pH of3 to 11, preferably 1 to 13, is solubility measured by use of waterprepared by adding nitric acid or potassium hydroxide to deionized waterand adjusting the pH of the solution. This definition applies to thefollowing description as well.

[0056] Further, the solubility of the water-soluble particles in waterat 50° C. is preferably 0.5 to 15 wt %, more preferably 0.7 to 12 wt %,particularly preferably 1 to 10 wt %. When the solubility is lower than0.5 wt %, pores may not be able to be formed sufficiently and thepolishing rate may be decreased as in the above case. Meanwhile, whenthe solubility is higher than 15 wt %, the rate of elution of thewater-soluble particles from the polishing pad may exceed the upperlimit undesirably as in the above case.

[0057] Further, the solubility of the above water-soluble particles inwater at 25° C. at a pH of 3 to 11, preferably 1 to 13, is 0.1 to 10 wt% and is within ±50%, preferably ±30%, more preferably ±20% ofsolubility thereof in water at 25° C. at a pH of 7. In particular, thesolubility of the water-soluble particles in water at 25° C. at a pH of3 to 11, preferably 1 to 13, is 0.1 to 3 wt %, particularly 0.5 to 2.5wt %, and is particularly preferably within ±50%, preferably ±30%, morpreferably ±20% of solubility thereof in water at 25° C. at a pH of 7.As long as a change in solubility by pH is within the above range,water-soluble particles present in the vicinity of the outermost layerof the polishing pad dissolve or swell and leave or free from thepolishing pad, thereby facilitating adequate formation of pores,regardless of pH at the time of polishing and even if the pH changesduring polishing.

[0058] Further, the elution rate of the water-soluble particlescontained in the polishing pad when the polishing pad is immersed inwater is preferably 0.05 to 50 wt %, more preferably 0.1 to 25 wt %,particularly preferably 0.2 to 10 wt %, at 25° C. Further, the elutionrate is also preferably 0.05 to 50 wt %, more preferably 0.1 to 25 wt %,particularly preferably 0.2 to 10 wt %, at 50° C. When the elution rateis lower than 0.05 wt %, pores may not be formed sufficiently, and adesired polishing rate may not be exerted. Meanwhile, when it is higherthan 50 wt %, pores may be formed even inside the polishing pad, thehardness of the polishing pad is lowered, and polishing properties suchas in-plane uniformity and local planarity may deteriorate undesirably.

[0059] The rate of elution to water is preferably 0.05 to 50 wt %, morepreferably 0.1 to 25 wt %, particularly preferably 0.2 to 10 wt %, at25° C. or 50° C. at a pH of 3 to 11, preferably 2 to 13. As long as theelution rate is within a given range in the above pH range, excessiveelution of the water-soluble particles can be inhibited, and onlywater-soluble particles present in the vicinity of the outermost layerof the polishing pad dissolve or swell and leave or free from thepolishing pad, thereby facilitating adequate formation of pores,regardless of pH at the time of polishing and even if the pH changesduring polishing. In addition, since deterioration in the hardness ofthe pad can also be inhibited, excellent polishing properties such asin-plane uniformity and local planarity are retained.

[0060] The rate of elution to water of the water-soluble particles at apH of 3 to 11, preferably 1 to 13, is the rate of elution measured byuse of water prepared by adding nitric acid or potassium hydroxide todeionized water and adjusting the pH of the resulting solution.

[0061] The rate of elution to water of the water-soluble particles canbe calculated as a value obtained by dividing the weight ofwater-soluble particles eluted into water when the polishing pad isimmersed in water (deionized water) whose weight is twice as much asthat of the pad at 25° C. for 12 hours, by the weight of water-solubleparticles contained in the polishing pad before immersion and thenmultiplying the quotient by 100.

[0062] In addition to the function of forming the pores, thewater-soluble particles have a function of increasing the indentationhardness of the polishing pad (e.g., Shore D hardness of 35 to 100).With high indentation hardness, pressure applied to a surface to bepolished by the polishing pad can be rendered high. Thereby, thepolishing rate is improved, and high polishing surface planarity is alsoachieved. Therefore, the water-soluble particles are particularlypreferably solid particles with which satisfactory indentation hardnesscan be secured in the polishing pad.

[0063] The sizes of the pores are preferably 0.1 to 500 μm, morepreferably 0.5 to 100 μm. When the sizes of the pores are smaller than0.1 μm, they are smaller than the particle diameters of abrasives insome cases, so that they become liable to hold th abrasives lesssufficiently. Meanwhile, when the sizes of the pores are larger than 500μm, satisfactory strength and indentation hardness are liable to becomedifficult to obtain.

[0064] In addition to the above water-insoluble matrix and water-solubleparticles, the polishing pad of the present invention may also containother compounding agents as required.

[0065] Illustrative examples of other compounding agents which can beincorporated into the polishing pad of the present invention include acompatibility-imparting agent, a filler, a surfactant, abrasives, asoftener, an antioxidant, an ultraviolet absorber, an antistatic agent,a lubricant, and a plasticizer.

[0066] Illustrative examples of the above compatibility-imparting agentinclude water-soluble polymers having two or more groups selected froman acid anhydride group, a carboxyl group, a hydroxyl group, an epoxygroup, an oxazoline group, an amino group and other groups in amolecule, and other coupling agents.

[0067] The above filler can be added to improve the rigidity of thepolishing pad. Illustrative examples of the filler include calciumcarbonate, magnesium carbonate, talc and clay.

[0068] Illustrative examples of the above surfactant include a cationicsurfactant, an anionic surfactant, and a nonionic surfactant. Specificexamples of the cationic surfactant include an aliphatic amine salt andan aliphatic ammonium salt. Specific examples of the anionic surfactantinclude aliphatic soap, carboxylates such as an alkyl ether carboxylate,sulfonates such as an alkyl benzene sulfonate, an alkyl naphthalenesulfonate and α-olefin sulfonate, sulfuric ester salts such as a higheralcohol sulfuric ester salt, an alkyl ether sulfate and apolyoxyethylene alkyl phenyl ether sulfate, and phosphoric ester saltssuch as an alkyl phosphoric ester salt. Specific examples of thenonionic surfactant include ether-type nonionic surfactants such as apolyoxyethylene alkyl ether, ether-ester-type nonionic surfactants suchas a polyoxyethylene ether of glycerine ester, and ester-type nonionicsurfactants such as a polyethylene glycol fatty acid ester, glycerineester and sorbitan ester.

[0069] The polishing pad of the present invention can contain abrasives.In that case, chemical machinery polishing can be performed bysupplying, for example, water, in place of a water-based dispersion forchemical machinery polishing. When the polishing pad of the presentinvention contains the abrasives, it is preferred that the pad contain,together with the abrasives, at least one selected from an oxidizingagent, an anti-scratching agent, a pH regulator and the like.

[0070] Illustrative examples of the above abrasives include particles ofsilica, alumina, ceria, zirconia and titania. These can be used alone orin combination of two or more.

[0071] Illustrative examples of the above oxidizing agent includehydrogen peroxide, peracetic acid, perbenzoic acid, organic peroxidessuch as t-butyl hydroperoxide, permanganic acid compounds such aspotassium permanganate, bichromic acid compounds such as potassiumbichromate, halogen acid compounds such as potassium iodate, nitric acidcompounds such as nitric acid and iron nitrate, perhalogen acidcompounds such as perchloric acid, persulfates such as ammoniumpersulfate, and heteropoly acids. Of these oxidizing agents, thepersulfates such as ammonium persulfate are particularly preferred, inaddition to the hydrogen peroxide and organic peroxides whosedecomposition products are harmless.

[0072] Illustrative examples of the above anti-scratching agent includebiphenol, bipyridyl, 2-vinylpyridine, 4-vinylpyridine, salicylaldoxime,o-phenylenediamine, m-phenylenediamine, catechol, o-aminophenol,thiourea, N-alkyl-group-containing (meth)acrylamide,N-aminoalkyl-group-containing (meth)acrylamide,7-hydroxy-5-methyl-1,3,4-triazaindolizine, 5-methyl-1H-benzotriazol,phthalazine, melamine, and 3-amino-5,6-dimethyl-1,2,4-triazine.

[0073] The above pH regulator is a component other than the above othercompounding agents and shows acidity or alkalinity upon contact withwater. Illustrative examples of such a pH regulator include acids otherthan those described above, ammonia, and hydroxides of alkali metals.Specific examples of the hydroxides of alkali metals include sodiumhydroxide, potassium hydroxide, rubidium hydroxide, and cesiumhydroxide.

[0074] A method of preparing a composition for forming the polishing padis not particularly limited. When the method comprises a kneading step,kneading can be performed by use of a known kneading machine.Illustrative examples of the kneading machine include a roll, a kneader,a Banbury mixer, and single-screw and multi-screw extruders. A kneadedcomposition for the polishing pad can be processed into a desired shapesuch as a sheet, a block or a film by carrying out press molding,extrusion, injection molding or the like. Further, by processing thecomposition having a desired shape to a desired size, the polishing padcan be obtained.

[0075] Further, the polishing pad can be obtained by kneading thewater-soluble particles and an uncrosslinked polymer together by theabove method, processing the obtained product to a desired shape, andcrosslinking the molded article by the above method. The heatingtemperature for crosslinking may be room temperature to 300° C.,preferably 50 to 200° C. Further, a composition containing thewater-soluble particles and the uncrosslinked polymer can be molded in amold and crosslinked. An article molded to a desired shape in advancecan be crosslinked.

[0076] Further, a method of dispersing the water-soluble particles inthe matrix material is not particularly limited. In general, however,the water-soluble particles can be dispersed by kneading theuncrosslinked polymer, the water-soluble particles and other additivesin the manner described above. In this kneading, the uncrosslinkedpolymer is kneaded under heating so as to be processed easily, and thewater-soluble particles are preferably solids at temperatures during thekneading. With the water-soluble particles in solid form, it isfacilitated to disperse the water-soluble particles such that they showthe above preferred average particle, regardless of the degree ofcompatibility thereof with the uncrosslinked polymer. Consequently, itis preferable to select the type of the water-soluble particlesaccording to the processing temperature of the uncrosslinked polymerused.

[0077] The Shore D hardness of the polishing pad of the presentinvention is preferably 35 to 100, more preferably 50 to 90, much morepreferably 60 to 85, as described above. When the Shore D hardness islower than 35, pressure applicable to a surface to be polished at thetime of polishing is liable to decrease, the polishing rate decreases,and polishing surface planarity may become insufficient.

[0078] On a surface, i.e., polishing surface of the polishing pad of thepresent invention, grooves and a dot pattern can be formed in a desiredshape as required so as to improve dischageability of slurry. Further,on the rear surface (surface opposite to the polishing surface) of thepolishing pad, a softer layer may be laminated so as to form a polishingpad having a multilayered structure. In addition, the shape of thepolishing pad is not particularly limited. A shape such as a disk, abelt or a roller can be selected as appropriate according to a polishingdevice. Furthermore, it is also possible to form a through-hole in thepolishing pad of the present invention and attach a window for end-pointdetection which has translucency.

[0079] The polishing pad of the present invention can be used in apolishing method of polishing the surfaces of various objects to bepolished. According to the polishing method, chemical machinerypolishing which is excellent in surface planarity can be carried out,and a high polishing rate can be attained.

[0080] The objects to be polished are not particularly limited, andvarious objects to be polished can be used. Illustrative examples of theobjects to be polished include an object to be polished which involves amaterial to be embedded and an object to be polished which involves nomaterial to be embedded.

[0081] An example of the object to be polished which involves a materialto be embedded is a laminate obtained by depositing a desired materialon the front surface of a board which is processed into a semiconductordevice having grooves at least on the front surface, by a method such asCVD such that the desired material is embedded at least in the grooves.The above board generally comprises at least a wafer and an insulatingfilm formed on a surface of the wafer. A stopper layer which serves as astopper at the time of polishing may be formed on the surface of theinsulating film. By polishing this object to be polished by use of thepolishing pad of the present invention, the excessively depositedmaterial to be embedded can removed, and the surface thereof can beflattened. When the object to be polished has the stopper layer underthe embedded material, polishing of the stopper layer can also becarried out at the late stage of polishing of the embedded material.

[0082] The material to be embedded is not particularly limited.Illustrative examples thereof include (1) an SiO₂-based insulatingmaterial used in an STI step, such as P-TEOS, PE-TEOS, O₃-TEOS, HDP-SiOor FSG (fluoridated SiO₂-based insulating film), (2) a material formetal wiring which is used in a damasin step and comprises at least oneof Al and Cu, (3) a material for via plugs which is used in a via plugformation step and comprises at least one of Al, Cu and W, (4) aninterlayer insulating film material used in an interlayer insulatingfilm formation step, as exemplified by an SiO₂-based insulating materialsuch as P-TEOS, PE-TEOS, O₃-TEOS, HDP-SiO or FSG, BPSG (materialprepared by incorporating B and/or P into SiO₂), Low-k (organic low-kinsulating material), SOG, and HSQ-SOG (hydrogen-containing porous SOG).Further, a stopper material constituting the above stopper layer may bea nitride-based material such as Si₃N₄, TaN or TiN.

[0083] Meanwhile, illustrative examples of the object to be polishedwhich involves no material to be embedded include polysilicon and baresilicon.

[0084] Further, an abrasive can be generally used in polishing theobject to be polished. It is preferable that the abrasive be selected asappropriate according to the type of the object to be polished. Forexample, a water-based dispersion may be used as the abrasive. Amaterial constituting the water-based dispersion is not particularlylimited. Illustrative examples of the material include those mentionedabove, such as water, abrasives, an oxidizing agent, a hydroxide of analkali metal, acid, a pH regulator, a surfactant, and an anti-scratchingagent. These can be used alone or in combination of two or more.

EXAMPLES

[0085] Hereinafter, the present invention will be further described withreference to Examples.

[0086] [1] Preparation of Composition for Polishing Pad and Molding ofPolishing Pad

Example 1

[0087] 80 vol % of 1,2-polybutadiene (product of JSR Corporation, tradename “JSR RB830”) which was crosslinked later to become a matrixmaterial and, as water-soluble particles, 20 vol % of β-cyclodextrin(product of BIO RESEARCH CORPORATION OF YOKOHAMA, trade name “DEXPALβ-100”; hereinafter, coupled β-cyclodextrin will be referred to as“modified β-cyclodextrin”) with an average particle diameter of 16 μmwhich had been coupled with 1 wt % ofγ-(2-aminoethyl)-aminopropyltrimethoxysilane in advance were mixedtogether in an extruder heated to 170° C. Thereafter, 0.3 parts byweight of organic peroxide (product of NOF CORPORATION, trade name“PERHEXIN 25B”) was added, and the resulting mixture was further mixedat 130° C. and then crosslinked and molded in a mold at 170° C. for 20minutes so as to obtain a polishing pad having a diameter of 60 cm and athickness of 3 mm.

[0088] The obtained pad had a weight of about 1 kg and contained 280 gof modified β-cyclodextrin. This pad and 2 kg of deionized water werecharged into a stainless steel container which was then placed in athermostatic chamber adjusted to 25° C., and the contents were stirredby means of a magnetic stirrer. After 12 hours, the pad was taken out ofthe container, and 1.5 g of eluate was extracted into an aluminum plateand dried for 30 minutes by a dryer adjusted to 200° C. After drying,the weight of solid (modified β-cyclodextrin) remaining in the plate was3.0 mg. From these numerical values, the elution ratio [(weight ofmodified β-cyclodextrin eluted by immersion/weight of modifiedβ-cyclodextrin contained in polishing pad)×100] of β-cyclodextrin elutedinto deionized water was calculated in the following manner. As aresult, the elution ratio was about 1.4 wt %. Further, the elution ratioobtained when the above experiment was repeated except that athermostatic chamber adjusted to 50° C. was used was about 1.5 wt %.Consequently, it is understood that a difference due to a difference intemperatures is very small.

[0089] Method of Calculating Elution Ratio: When a total elution amountis x (g) and the weight of solid remaining in the plate is y (3.0 mg),x/(2000+x)=(y/1000)/1.5 holds, and x is 4.008 g. Accordingly, theelution ratio is calculated as (4.008/280)×100=1.428 or about 1.4%.

[0090] The solubility of the coupled modified β-cyclodextrin in waterwas 2.3 wt % at 25° C. and 4.9 wt % at 50° C. The pH dependency of thesolubility at 25° C. of the modified β-cyclodextrin is shown in FIG. 1.According to FIG. 1, solubilities at pHs of 3, 5, 7, 9 and 11 were 2.4wt %, 2.5 wt %, 2.5 wt %, 2.7 wt % and 2.6 wt %, respectively. Further,solubilities at pHs of 3, 5, 9 and 11 were −4%, 0%, +8% and +4% based onsolubility at a pH of 7, indicating that a change in solubility at a pHof 3 to 11 is very small. Adjustment of the pH was made by use of nitricacid or potassium hydroxide.

[0091] Then, on the polishing surface of the polishing pad, a pluralityof circular grooves with an average of groove widths of 0.5 mm, anaverage of groove depths of 1 mm and an average of pitches of 1.75 mmwere formed concentrically by use of an original groover of KATO KIKAICO., LTD. Then, the polishing properties of the polishing pad wereevaluated in the following manner.

[0092] (1) Polishing Rate and Presence/Absence of Scratches

[0093] The polishing pad was placed on the surface plate of a polishingdevice (product of SFT CO., LTD., model “LAP MASTER LM-15”), therevolution speed of the surface plate was set at 50 rpm, and an SiO₂film wafer was polished for 2 minutes by using a slurry for chemicalmachinery polishing diluted to 3 times (product of JSR Corporation,trade name “CMS 1101”) at a flow rate of 100 cc/min so as to evaluate apolishing rate and the presence or absence of scratches. The polishingrat was calculated by measuring the thickness of the film before andafter polishing by use of an optical thicknessmeter and dividing adifference between the thicknesses by a polishing time. Further, thepresence or absence of scratches was confirmed by observing the polishedsurface of the SiO₂ film wafer after polishing under an electronmicroscope. As a result, the polishing rate was 350 nm/min, andscratches were hardly observed.

[0094] (2) Evaluation of Dishing

[0095] After a semiconductor water (product of SKW CO., LTD., trade name“SKW-7”) was polished under the following conditions, dishing wasmeasured by use of a fine shape measuring device (product of KLA-TencorCo., Ltd, model “P-10”). As a result, the dishing was 70 nm, and thepolished surface had excellent surface planarity.

[0096] Slurry: CMS 1101 (product of JSR Corporation)

[0097] Chemical Machinery Polishing Device: EPO 112 (product of EbaraCorporation)

[0098] Slurry Feed Rate: 200 ml/min

[0099] Polishing Load: 400 g/cm²

[0100] Revolution Speed of Surface Plate: 70 rpm

[0101] Revolution Speed of Head: 70 rpm

[0102] Polishing Rate: 400 nm/min

[0103] Polishing Time: 5.75 min (15% over polish)

Example 2

[0104] 60 parts by volume of uncrosslinked 1,2-polybutadiene (product ofJSR Corporation, trade name “JSR RB830”), 20 parts by volume ofuncrosslinked ethylene-vinyl acetate copolymer (product of TOSOHCORPORATION, trade name “ULTRASEN 630”), and 20 parts by volume ofβ-cyclodextrin (product of BIO RESEARCH CORPORATION OF YOKOHAMA, tradename “DEXPAL β-100”, average particle diameter: 20 μm) as water-solubleparticles were mixed together by use of a twin-screw extruder adjustedto 160° C. There after, 1.0 parts by weight of organic peroxide (productof NOF CORPORATION, trade name “PERCUMYL D40”) was added, and theresulting mixture was further mixed and then extruded into a mold. Then,the mixture was kept at 170° C. for 18 minutes so as to be crosslinked,thereby obtaining a polishing pad having a diameter of 60 cm and athickness of 3 mm. Thereafter, on the polishing surface of the polishingpad, a plurality of circular grooves with an average of groove widths of0.5 mm, an average of groove depths of 0.5 mm and an average of pitchesof 4 mm were formed concentrically by use of an original groover of KATOKIKAI CO., LTD. Then, a polishing rate, the presence or absence ofscratches and dishing were evaluated in the same manner as in Example 1.As a result, the polishing rate was 300 nm/min, scratches were hardlyobserved, the dishing was 60 nm, and the polished surface had excellentsurface planarity.

Comparative Example 1

[0105] A polishing pad having a diameter of 60 cm and a thickness of 3mm was obtained in the same manner as in Example 1 except that potassiumsulfate having an average particle diameter of 20 μm (product ofTakasugi Pharmaceutical Co., Ltd.) was used as water-soluble particles.Further, when the degree of elution to water of potassium sulfate wascalculated in the same manner as in Example 1, it was 80 wt %. Theelution rate when the same experiment was conducted in water at 50° C.was 82 wt %. The solubility of potassium hydroxide was 11 wt % at 25° C.and 12 wt % at 50° C. Further, on the polishing surface of the polishingpad, a plurality of circular grooves similar to those of Example 1 wereformed concentrically by use of an original groover of KATO KIKAI CO.,LTD. Then, a polishing rate, th presence or absence of scratches anddishing were evaluated in th same manner as in Example 1. As a result,the polishing rate was 300 nm/min and acceptable. However, a number ofscratches were observed, the dishing was 180 nm, and the polishedsurface had poor surface planarity.

Comparative Example 2

[0106] On the polishing surface of a commercially available polishingpad (product of Rodel & Nitta Co., Ltd., trade name “IC1000”) made of apolyurethane foam, a plurality of circular grooves similar to those ofExample 1 were formed concentrically by use of an original groover ofKATO KIKAI CO., LTD. Then, a polishing rate, the presence or absence ofscratches and dishing were evaluated in the same manner as in Example 1.As a result, the polishing rate was 350 nm/min and acceptable. However,a number of scratches were observed, the dishing was 150 nm, and thepolished surface had poor surface planarity.

[0107] As described above, in the polishing pad of the presentinvention, pores are formed in good conditions, the pores are notblocked by dressing, and slurry retainability is good, even when variousslurries having different pHs are used within a wide pH range. Further,contained water-soluble particles neither absorb moisture nor swell, andthe polishing pad can have a high degree of hardness, a high polishingrate, and good polishing properties such as surface planarity.

[0108] Further, if the solubility in water at 50° C. of thewater-soluble particles and the elution ratio at 50° C. of thewater-soluble particles when the polishing pad is immersed in water arewithin specific ranges, the polishing pad can have better polishingproperties.

[0109] Further, if the solubility in water at 25° C. of thewater-soluble particles at a pH of 3 to 11 is within a specific range,the polishing pad can have better polishing properties.

[0110] Further, when the water-insoluble matrix material contains acrosslinked 1,2-polybutadiene, an elasticity restoration property isimparted to the pad, the pores are not blocked, and the polishing padcan have better properties including surface planarity.

[0111] In the polishing pad of the present invention in which thewater-soluble particles have an amino group, an epoxy group, anisocyanurate group or a hydroxyl group, pores are formed in goodconditions, the pores are not blocked even by dressing, and slurryretainability is good. Further, the solubility of the water-solubleparticles in water can be adjusted easily by a proper range, moistureabsorption and swelling of the water-soluble particles in the pad can besuppressed, and the polishing pad can have a particularly high degree ofhardness, a high polishing rate and good polishing properties such assurface planarity.

What is claimed is:
 1. A polishing pad comprising: a water-insolublematrix material comprising a crosslinked polymer, and water-solubleparticles dispersed in the water-insoluble matrix material, wherein thesolubility of the water-soluble particles in water is 0.1 to 10 wt % at25° C., and the amount of water-soluble particles eluted from the-padwhen the pad is immersed in water is 0.05 to 50 wt % at 25° C.
 2. Thepad of claim 1, wherein the solubility of the water-soluble particles inwater is 0.5 to 15 wt % at 50° C., and the amount of water-solubleparticles eluted from the pad when the pad is immersed in water is 0.05to 50 wt % at 50° C.
 3. The pad of claim 1, wherein the solubility ofthe water-soluble particles in water is 0.1 to 3 wt % at 25° C. at a pHof 3 to
 11. 4. The pad of claim 1, wherein the crosslinked polymer ofthe water-insoluble matrix material is a crosslinked 1,2-polybutadiene.5. A polishing pad comprising: a water-insoluble matrix materialcomprising a crosslinked polymer, and water-soluble particles dispersedin the water-insoluble matrix material, wherein the solubility of thewater-soluble particles in water is 0.1 to 10 wt % at 25° C. at a pH of3 to 11, and solubility thereof in water at 25° C. at a pH of 3 to 11 iswithin ±50% of solubility thereof in water at 25° C. at a pH of
 7. 6. Thpad of claim 5, wherein the solubility of th water-soluble particles inwater is 0.1 to 3 wt % at 25° C. at a pH of 3 to 11, and solubilitythereof in water at 25° C. at a pH of 3 to 11 is within ±50% ofsolubility thereof in water at 25° C. at a pH of
 7. 7. The pad of claim5, wherein the crosslinked polymer of the water-insoluble matrixmaterial is a crosslinked 1,2-polybutadiene.
 8. A polishing padcomprising: a water-insoluble matrix material comprising a crosslinkedpolymer, and water-soluble particles dispersed in the water-insolublematrix material, wherein the water-soluble particles contain at leastone group selected from the class consisting of an amino group, an epoxygroup, an isocyanurate group and a hydroxyl group.
 9. The pad of claim8, wherein the solubility of the water-soluble particles in water is 0.1to 10 wt % at 25° C. at a pH of 3 to 11, and the amount of water-solubleparticles eluted from the pad when the pad is immersed in water is 0.05to 50 wt % at 25° C. at a pH of 3 to
 11. 10. The pad of claim 8, whereinthe solubility of the water-soluble particles in water is 0.1 to 10 wt %at 25° C. at a pH of 3 to 11, and solubility thereof in water at 25° C.at a pH of 3 to 11 is within ±50% of solubility thereof in water at 25°C. at a pH of
 7. 11. The pad of claim 10, wherein the solubility of thewater-soluble particles in water is 0.1 to 3 wt % at 25° C. at a pH of 3to 11, and solubility thereof in water at 25° C. at a pH of 3 to 11 iswithin ±50% of solubility thereof in water at 25° C. at a pH of
 7. 12.The pad of claim 8, wherein the crosslinked polymer of thewater-insoluble matrix material is a crosslinked 1,2-polybutadiene.